Waste combustion system



March 10, 1970 B. G. ALTMANN 3,499,400

WASTE COMBUSTION SYSTEM 2 Sheets-Sheet 1 Filed June 5, 1968 \m mm IH MIHI IH A TTOP/VEY March 10, 1970 B. ALTMANN 3,499,400

' WASTE COMBUSTION SYSTEM I I Filed June 5, 1968 2 Sheets-Sheet 2 I'IIEI E 55,070 6.41 rm/v/v INVENTOR.

United States Patent O "ice 3,499,400 WASTE COMBUSTION SYSTEM Berton G. Altmann, Los Gatos, Calif., assignor to Kaiser Aluminum & Chemical Corporation, Oakland, Calif., a corporation of Delaware Filed June 3, 1968, Ser. No. 734,045 Int. Cl. F23g 23/00; F23] 1/00; F23c 7/.00 US. Cl. 110-8 8 Claims ABSTRACT OF THE DISCLOSURE Waste combustion system wherein solid or semi-solid waste is fed to a closed combustion chamber into which limited amounts of oxidizer (e.g., air) are fed to effect gasification of the waste. The chamber contains a fluid pressure sensing means operatively connected to the means for feeding fluid oxidizer whereby, if the pressure in the chamber falls below a preselected value, further oxidizer is fed to the chamber and whereby, if the pressure in the chamber exceeds a certain preselected value, the amount of oxidizer fed to the chamber is reduced. The

gaseous products of the limited combustion in the chamher, which gases are further combustible, are led to a further treating means, for example an afterburner, wherein they are fully oxidized. The oxidizer (e.g., air) input to this afterburner can also be operatively connected to the pressure sensing means whereby when the pressure in the chamber exceeds a certain preselected value, increased amounts of oxidizer are fed to the afterburner.

BACKGROUND OF THE INVENTION This invention concerns a system for the efficient combustion of solid or semi-solid combustible materials, more particularly waste material.

Combustion or incineration of Waste materials has long been practiced. However, in recent years there has been an increasing awareness of the air pollution resulting from uncontrolled burning of waste. Accordingly, it is now desired that when waste materials are burned, the combustion be controlled and carried out in such a manner that a minimum of objectionable air pollutants is discharged into the atmosphere.

It is known that conducting combustion in a first chamber to gasify solid waste, followed by further oxidation of the gaseous products to effect their complete combustion, results in an eflicient combustion system which can be operated to discharge little objectionable waste. However, while it is possible to operate such a system efliciently when the load of combustible waste is uniform and constant, in most actual incineration systems the load of waste to be burned varies greatly in amount, type, moisture content, and other characteristics. Accordingly, it is a problem to obtain efiicient, complete combustion of the waste under widely varying conditions of load. It is the solution of this problem to which the present invention is directed.

SUMMARY OF THE INVENTION It has now been found, according to this invention, that efficient combustion of waste material can be achieved under widely varying conditions of load and type of waste in a system comprising: (1) closed chamber means wherein waste can be oxidized to fluent intermediate products of combustion which can be further oxidized; (2) means for feeding waste into said chamber; (3) means for feeding fluent oxidizer into said chamber; (4) fluid pressure responsive means responsive to the fluid (e.g., gas) pressure in said chamber and operatively 3,499,400 Patented Mar. 10, 1970 connected to said oxidizer feeding means for regulating the oxidizer feeding means whereby when the pressure in the chamber drops below a preselected value, the amount of oxidizer fed to the chamber is increased and whereby, when the pressure in the chamber exceeds a preselected value, the amount of oxidizer fed to the chamber is decreased; and (5) conduit means connecting the chamber with (6) a further waste material treating means, for example an afterburner.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a side elevation view, partially in section, of a combustion system according to this invention;

FIGURE 2 is a partially sectioned view taken along the line 22 of FIGURE 1; and

FIGURE 3 is a sectional view along the line 33 of FIGURE 1.

DETAILED DESCRIPTION It will be understood that the following description, and the accompanying drawings, illustrate one advantageous embodiment of this invention. However, the particular structure described is merely illustrative of the invention, the scope of which is defined by the appended claims.

The apparatus according to this invention comprises a closed chamber 11 constructed of a circular steel shell 12 which is lined with refractory material 13, and having a back wall 15 and a front door 10. Shell 12 is supported on legs 14.

In the side of chamber 11 is an opening 16 through which waste material can be fed. Opening 16 is closed by door 17 which slides along the length of chamber 11 in upper and lower tracks 18 and 18' to open and close opening 16. The purpose of door 17 is to close chamber 11 so as to minimize leakage of air into it.

Immediately adjacent opening 16, and in sealed relationship thereto, is a feeding means, feeding means, generally indicated by 19. As illustrated in the drawing, it comprises a U-shaped trough 21 closed at the top by a lid 22 which can be raised so that waste material can be placed in trough 21. At the end of trough 21 remote from opening 16 is a pusher plate 23 which substantially fills the cross section of trough 21 and which can be moved longitudinally within feeding means 19 to push waste through opening 16 into chamber 11. Such longitudinal motion can be achieved by pushing pusher rod 24, attached to pusher plate 23, in through collar 26 which is carried by end plate 27 which in turn is attached to U-trough 21. Such pushing motion can be by manual operation or, for example, by hydraulic means. In general, feeding means 19 will be constructed to minimize air leakage into chamber 11 when waste is being charged.

Alternatively, an automatic feeder such as that disclosed in my copending application with John D. Bailey for Material Handling Apparatus for Effecting Compaction of Material and Removal Thereof, filed concurrently With this application, can be used in conjunction with the incinerator of this invention.

Outside chamber 11 is an air or other fluent oxidizer feeding means 28, which may comprise a conventional blower and plenum. Such apparatus being well known, it is not illustrated in detail. Air feeding means 28 is connected by means of conduit 29 to holes 31 and 31 in the back wall 15 of chamber 11. Openings 31 and 31 permit air fed through conduit 29 from feeding means 28 to enter chordal plenum chambers 32 and 32' at the bottom of chamber 11. Plenum chambers 32 and 32' are formed by chordal refractory sections 33 and 33' supported on metal supports 34 and 34 spanning a chordal section of steel 3 shell 12. Refractory sections 33 and 33 can be constructed of preformed refractory shapes 36 into which have been cut small holes 37 through which combustion air is admitted to the interior of chamber 11.

While holes 37 have been shown as being at right angles to the surfaces of chordal refractory sections 33 and 33', it will be understood that other angles can be used. For example, holes 37 can be horizontal.

One advantage of this construction is that the velocity of the air, or other fluent oxidizer, entering combustion chamber 11 is low and therefore there is little entrainment of solid materials which might be swept out the stack (not shown) of the incinerator as ash or smoke. Another advantage of this construction is that chordal sections 33 and 33 act as ash receiving grates and the air coming up through holes 37 tends to levitate or fluidize the ash, causing it to be conveyed downwardly toward the bottom of chamber 11 whence it can be removed through ash removal port 38. If, as was previously sug- I gested, holes 37 are horizontal, the action of sweeping the ash toward port 38 will be even more pronounced, especially at low loads of material in the incinerator. As will be clear, port 38 is normally closed by means of door 39 which can be opened and closed by sliding in tracks 41 and 41'. Preferably, ash is discharged into a container 53 within a closed vestibule 54. Thus, ash can be discharged while the incinerator is in operation without admitting excess air. After door 39 is closed, container 53 can be removed from chamber 54 through a door (not shown).

Within chamber 11 is a pressure sensing means 42, responsive to the gas pressure in chamber 11. Pressure sensing means 42 is operatively connected to control 43 which in turn is operatively connected to a motor 44 which opens and closes valve 46 in feed line 29. Controller 43 operates so that if the pressure in chamber 11 drops below a preselected value, valve 46 is opened wider to admit more air to chamber 11, which results in more oxidation of the waste, consequently increased temperature, and thus increased formation of gaseous products of combustion, which will raise the gas pressure in chamber 11. Conversely, if the gas pressure in chamber 11 exceeds a preselected value, controller 43 operates to close valve 46 somewhat, reducing the amount of air fed to chamber 11 and consequently reducing the rate of combustion therein. As an example of a specific embodiment of the invention, a Dwyer Model 1640 diaphragm type double-throw, null position switch can be used to control a reversing electric motor which actuates a butterfly valve in conduit 29.

The gaseous products of combustion formed in chamber 11, which are capable of further oxidation, are led out through exit 47 to a further waste material treating means which, in the embodiment shown, can be an afterburner 48. Afterburner 48, which can be of any construction known in the art, has means for feeding fluent oxidizer (e.g., air) to the combustible waste gases whereby they are completely oxidized. Conventionally, afterburner 48 will include means for adding heat to the combustible waste gases, for example a gas or oil burner or an electric heating coil, to raise their temperature to the point where they will burn when admixed with air. As is well known in the art, this heat input means may be needed only during the initial startup of the incinerator, after which time the temperature of the waste gases from main combustion chamber 11 will be high enough so that no further input of heat is required.

An afterburner which is particularly suited for use in the practice of this invention is that disclosed and claimed in my copending application with John D. Bailey for Waste Combustion Afterburner, said application having been filed concurrently with the present application.

As was mentioned, air is fed to afterburner 48 to further consume the waste products of combustion formed in chamber 11. The air can be supplied from air feeding means 28 by means of conduit 49. If desired, control means 43 can be operatively connected with motor 51 which opens and closes valve 52 in conduit 49. When this auxiliary method of control is used, controller 43 will be operatively connected with motor 51 so that when the gas pressure in chamber 11 exceeds a certain preselected value, indicating a higher generation of gas in chamber 11, which gas must subsequently be consumed in afterburner 48, then motor 51 will open valve 52 wider to admit more air to afterburner 48. Conversely, when the gas pressure in chamber 11 drops below a certain preselected value, indicating a smaller generation of combustible gases, then motor 51 will close valve 52 somewhat, reducing the amount of air fed to afterburner 48. It will be understood, however, that this auxiliary method of control of the air fed to the afterburner is optional and not essential to the practice of the present invention.

In operating the incinerator system with an afterburner including heat input means, it will generally be found convenient to ignite or otherwise activate the heat input means of the afterburner to create a draft in the incinerator. However, this is not essential. In any case, waste material to be burned will be loaded into chamber 11 and ignited. Such initial ignition can be by hand, for example through port 20 in front door 10, or by special ignition means (not shown) built into the system. If not already operating, the afterburner will be activated when the waste is initially ignited in chamber 11. Simultaneously, air feeding means 28 will be activated to feed air to chamber 11 and afterburner 48. Controller 43 will be adjusted so that the amount of air fed to chamber 11 is sufficient to burn the solid or semi-solid waste to a gaseous condition, but insufficient in amount to completely oxidize these gaseous products, which will move into afterburner 48 and be completely oxidized therein. After initial startup, the operation of the incinerator system is completely automatic. As waste is fed to chamber 11, controller 43 will maintain the input of air to chamber 11 so as to maintain the preselected pressure or pressure range therein. It will generally be found most convenient to operate the system with the pressure negative (i.e., below atmospheric) but as close to zero (i.e., atmospheric) as possible. In other words, as much air will be fed to chamber 11 as is possible without creating in chamber 11 a pressure above that of the outside atmosphere. In this way, the very slight negative pressure within chamber 11 will prevent leakage of smoke through any openings in chamber 11, for example while waste material is being charged through feed opening 16, while at the same time maintaining the maximum rate of combustion.

It will be understood that in the initial combustion of waste materials, much gas is generated due to the driving off of water and other voaltiles in the waste. However, as combustion proceeds, and the volatiles are driven off, the remaining solid material will be largely carbon, which will require more air for its combustion. This increased amount of air is automatically fed to the system of this invention since, after the volatiles are driven ofi, the pressure Within chamber 11 will tend to fall and consequently increased amounts of air will be fed to it.

It will be understood that, if desired, it is possible to extract the waste heat in the combustion gases leaving the incinerator system, for example in a heat exchanger (not shown), and use it, for example to preheat the air fed to main combustion chamber 11.

What is claimed is:

1. A combustible waste handling system wherein waste material can be oxidized comprising (a) closed chamber means wherein waste can be oxidized to fluent intermediate products of combustion which can be further oxidized;

(b) means for feeding waste into said chamber means;

(c) means for feeding fluent oxidizer into said chamber means;

(d) :fluid pressure responsive means responsive to the gas pressure in said chamber means and operatively connected to said oxidizer feeding means for regu lating the oxidizer feeding means whereby when the pressure in said chamber means drops below a preselected value, the amount of oxidizer fed to said chamber means is increased, and whereby, when the pressure in said chamber means exceeds a preselected value, the amount of oxidizer fed to said chamber means is decreased.

2. A system according to claim 1 comprising in addition (e) conduit means connecting said chamber means with (f) further waste material treating means.

3. A system according to claim 2 wherein said further waste material treating means is an afterburner to which fluent oxidizer is fed.

4. A system according to claim 3 wherein fluid pressure responisve means is operatively connected to means for feeding fluent oxidizer to said afterburner whereby, when the pressure in said chamber means exceeds a preselected value, the amount of oxidizer fed to the afterburner is increased.

5. A system according to claim 1 wherein said oxidizer feeding means comprises at least one plenum chamber located at the bottom of said chamber means, said plenum chamber having holes adapted to convey fluent oxidizer into said chamber means.

6. A system according to claim 5 wherein said chamber means is of circular section and said plenum chamber is a chordal chamber.

7. A system according to claim 6 wherein said oxidizer feeding means comprises two symmetrically disposed chordal plenum chambers.

8. A system according to claim 1 wherein said oxidizer feeding means is an air feeding means.

References Cited UNITED STATES PATENTS 3,323,475 6/1967 Melgaard 110-18 3,403,645 10/1968 Flowers l10l8 FOREIGN PATENTS 865,901 4/1961 Great Britain.

KENNETH W. SPRAGUE, Primary Examiner US. 01. X11. 110-7; 

